A headway regulated cruise control system of the general type under consideration is also known as ACC (adaptive cruise control, adaptive speed control). A headway regulated cruise control system influences the state of motion of the motor vehicle, taking into account the distance with respect to a preceding vehicle. Using a multiplicity of sensor data, such as the vehicle's own speed and the speed relative to the preceding vehicle, the headway regulated cruise control system cuts back the power of the engine or actively initiates braking if the distance with respect to the vehicle in front falls below a predetermined threshold value.
Headway regulated cruise control serves to assist the driver and should be distinguished from autonomous emergency braking systems. Such an emergency braking system is an electronic system designed to trigger an autonomous full braking operation independently of the driver. In contrast, a headway regulated cruise control system has a limiting retardation, which must not be exceeded by an action of the system on the motor vehicle. In other words, the headway regulated cruise control system cannot automatically brake the motor vehicle more sharply than is allowed by the limiting retardation.
In order to request the driver to reassume control of the vehicle from the headway regulated cruise control system in good time because the latter would be overloaded by the current traffic situation, the headway regulated cruise control system produces a motion prediction. A motion prediction is a mathematical model that extrapolates from the operating data of the motor vehicle, such as driving data in the form of the speed of the vehicle and its acceleration, and data on the distance with respect to a preceding vehicle, in particular the distance with respect to the preceding vehicle in future. In the case of known headway regulated cruise control systems, a warning is issued to the driver of the motor vehicle if the motion prediction shows that an acceleration greater than the predetermined limiting retardation is necessary to avoid a collision with the vehicle in front.
A disadvantage with known headway regulated cruise control systems is that they can lull the driver into a false sense of security if a warning is not issued even though intervention by the driver is urgently necessary.